The present invention relates to a dual-circuit pressure control valve for use in hydraulic brake systems for automotive vehicles comprising two control pistons which are arranged in a parallel side by side relationship each assigned to a different brake circuit and which are loaded by a common, adjustable preloading force, with the preloading force acting on the control pistons by means of a lever which is supported at a mounting at the housing of the pressure control valve and is tiltable at least around an axis extending parallel to the direction of displacement of the control pistons and additionally around the longitudinal axis of the lever.
In copending U.S. patent application Ser. No. 160,523, filed June 18, 1980, assigned to the same assignee as the present application, a dual-circuit pressure control valve with a change-over point adjustable from the outside is described, in which the lever is supported at the housing in a spherical joint and a compensating effect is, therefore, rendered possible in each direction. This pressure control valve is characterized by simple construction and ease of assembly and remedies tolerance and adjustment problems inherent in former arrangements.
Dependent on the composition of the surfaces of the two components movable in one another in the spherical joint, a specific friction moment may occur when tilting the lever, which moment is able to be eliminated by an appropriate surface treatment. Additionally, the sliding ability of the two surfaces may be impaired in the course of time by dirt or oxidation which also causes a certain friction moment during the tilting of the lever. As a consequence, this may result in a pressure difference of several bar in the two brake circuits.